The art of friction drives is very old and very extensive. I covered some of this art in my co-pending patent application Ser. No. 08/202,164 filed Feb. 25, 1994 now U.S. Pat. No. 5,407,399. In that application I explained the basic theory that the only two bodies that can roll on each other without spin are two cones that have their apexes at a common point. More than two cones can roll on each other without spin if their apexes all meet at one point.
There are many patents or variable speed drives where one element can be located on various points of another element so as to obtain variable speed ratios. I found three patents, U.S. Pat. Nos. 3,158,041, 5,014,565, and French 1,003,009, that note that two friction elements must have a common apex for proper rotation on each other. Unfortunately for the inventors, all three of these patents use curved "cones" in contact with the rollers (a technically correct cone is only one generated by a straight line). Such curved "cone" arrangements can produce proper mutual rolling but only if the rollers contact the curved "cones" at very small areas.
The circular area of a roller rolling on a curved cone must be very narrow. If this area is increased, the rolling develops spin or slip because the "cone" surface is no longer such that various contact elements of the curved "cone" have a common apex.
Two Russian patents show rollers contacting disks so that the rotary axes of the rollers pass through the center point of the disks that the rollers are contacting. The Russian patents are No. 1237-827to Nechitailo and No. 1562-565 to Ivashchenko. Both patents show very difficult-to-implement mechanisms in making the rollers move over the surface of the disks so as to vary the speed ratios. Instead of tipping the cone/s, as I do in my co-pending application Ser. No. 08/202,164 now U.S. Pat. No. 5,407,399 and in this application and keeping the roller on a fixed axis, the Russian patents show the roller axes as being constantly changed as the rollers are moved either toward or away from the center of the disks they contact.